The electric storage device comprises a plurality of electrically connected electric storage elements. There are an individual difference, a difference in degradation, and the like among a plurality of electric storage elements. For this reason, in the background art, e.g., the technique disclosed in Patent Literature 1, an abnormality in a plurality of electric storage elements is detected so as not to be affected by an individual difference, a difference in degradation, or the like among a plurality of electric storage elements. Specifically, from a state where the capacity of each electric storage element is equalized, each electric storage element is discharged by the same amount and a subsequent voltage drop in each electric storage element is detected so as to determine an abnormality of the electric storage element.